The present disclosure relates to a power storage apparatus as well as to an electric vehicle that utilizes power from a power storage apparatus.
Recently, secondary batteries such as lithium-ion batteries have been rapidly expanding to applications such as storage batteries for automobiles and power storage apparatus in which secondary batteries are combined with an alternative energy system such as solar cells or wind turbines. In the case of using a large number of storage elements such as unit cells (also called electrical cells or simply cells, and designated battery cells as appropriate in the following description) in order to produce a large output, a configuration is adopted in which a plurality of storage modules are connected in series. A storage module contains battery blocks in which a plurality of battery cells (four, for example) are connected in parallel and/or in series. A large number of battery blocks are enclosed in an outer case to form a storage module (also called an assembled battery).
There also exists a battery system in which a plurality of storage modules are connected, and in which a control apparatus shared by the plurality of storage modules is provided. Each storage module includes a module controller, with communication between the module controllers and the control apparatus realized via a communication unit or other means.
In the case of using a plurality of battery cells, in some cases one of the plurality of battery cells will reach the low-voltage threshold even though other battery cells have not yet reached the low-voltage threshold, due to factors such as differences in self-discharge among the battery cells. If the battery cells are once again charged in such a state, a problem occurs in that a battery cell may not be sufficiently charged, and battery cell performance may not be sufficiently exhibited.
In order to compensate for such disparities among plural battery cells, battery cell balancing is typically conducted. Controlling cell balancing involves acquiring voltage information for a plurality of battery cells. Japanese Unexamined Patent Application Publication No. 2010-081756 describes a configuration for acquiring battery information from a battery cell.